R&D Report 1962-06 : The Visibility of small brightness differences in television displays. G.F. Newell, W.K.E. Geddes This report describes measurements of the smallest brightness difference which can be reliably identified in television displays. The amplitude of the brightness difference is plotted as a function of the brightness level at which it can be just recognized. An estimate is made of the number of discrete levels into which a television picture should be quantized in order to preserve an acceptable picture quality without an unduly large number of levels.